This research contributes to the solution of the folding problem, the prediction of the spatial structure of a protein from the amino acid sequence of its polypeptide chain. In deference to the magnitude of the folding problem, this project considers the prediction of a common spatial protein substructure, the o'-helix. The proposed research will investigate the contribution of side-chain/polypeptide backbone hydrogen bonding interactions (capping) in the terminal regions of a helix which both terminate and stabilize the helical structure. The effect of systematic amino acid residue replacements on the helical content of model peptides will be evaluated using both circular dichroism and NMR measurements. These effects- expressed as AA G values, will be introduced into contemporary algorithms for prediction of helical structure.